I can’t disagree with your points. But, I think the key question is: "Did the customer get their money’s worth?" We have to recognize the intangibles in this equation: "owning the best of the best" or at the very least not having your "audiophile" friends look down on you because you don’t own "real hifi gear" -- the stuff the industry gurus say is pretty spectacular, Having a nice "trophy" sitting in the room is ample justification for some. Its not the "wrong" answer for those with the means to do so.
As I dealer, part of our Mission Statement was "Help people reward themselves for being successful." Some days it was a $12.95 wiring harness for a car stereo system. Other days it was a $1M fully automated home with high end home theater. From my perspective, it was unethical to deny someone the opportunity to audition better gear. Something a step (or two) above the price point they were interested in. No pressure. Just expanding their experiences with what high(er) performance audio can do.
For some, a $100k upgrade represents less than 1/10 of 1% of their net worth. A good call. As long as, in their minds, they're getting their money’s worth.
By the way, I own some old cars and a couple of older homes. I do most of the maintenance myself. I get the tool thing.